Understanding MIDI and Instruments


Any music that you create can be played through an instrument. An instrument can be anything from a sound card in a computer to a sophisticated external synthesizer. All instruments translate signals from the computer into specific musical equivalents. Different instruments synthesize sounds which can be dramatically different from one another. The problem of how to ensure that the resulting performance really sounds the way the composer (or arranger) intended requires the adoption of a standard set of sounds, shared by software and hardware vendors alike.



The First Standard


The first such standard was called General MIDI (GM), a set of definitions for MIDI program changes. Under this standard, for example, program change 0 is always a piano, program change 23 is always a harmonica, and so on. Other extensions to General MIDI were later created by Roland Corporation (GS) and Yamaha International (XG). In all cases, the goal is the same: to agree on a numbering scheme so that compositions sound more-or-less the same as they are performed on different instruments.



Other Supported Standards


These standards are only half the story, however. Many instruments support standards such as GM, GS and XG, but also offer additional sounds or features that are unique to each instrument. The precise manner in which each instrument responds to the computer's instructions may differ from instrument to instrument. To solve this problem a special text file isUsed to describe the mapping between certain MIDI messages and the desired outcome for a specific device.


There are actually 2 different instrument map files required to describe an instrument completely - one to describe melodic sounds and one to describe percussive sounds. This is because many percussive instruments do not have anything that could be described as a "pitch" (what is the pitch of a hand clap?) -- most instruments instead utilize each pitch value to represent a different percussive sound. These "drum maps" are also quite specific to each instrument and are usually displayed with a specific symbol or notehead type. You can edit the drum map to automatically associate display styles with percussive values -- see the Notation Options for more details.


Nearly every instrument you find these days supports General MIDI, so the map files for General MIDI instruments is the default. If you are using, say, a Roland SC-88 Pro or a Yamaha synth, it makes sense toUse appropriate map files so that you have access to all the features and sounds for your device. To change the map files for a device, select Options Sequencer… command from the menu, display the MIDI Out tab, and then select the Properties button for the selected device.



Note that the terms instrument and device have beenUsed interchangeably in these discussions. For the most part a device is the piece of hardware through which MIDI instructions are sent, whereas an instrument is the actual equipment that translates MIDI messages into sounds. The MPU-401 device on your sound card, for example, may be connected with a MIDI cable to your K-2000 keyboard, which creates the actual sounds. When viewing routing connections with the Track Properties Palette you can view the connections by device name or by instrument.